1. Field of the Invention
The present invention generally relates to a microelectromechanical system (MEMS) structure and a fabricating method thereof, in particular, to a MEMS structure having high thermal stability and a fabricating method thereof.
2. Description of Related Art
A microelectromechanical system (MEMS) structure is a microelectromechanical device fabricated by using a microprocessing technique. Due to its advantages in light weight and small size, the MEMS structure well satisfies the current requirements for light, thin, short, and small electronic products, and is studied in many fields. The existing MEMS structures include accelerometers, switches, capacitors, sensors, microphones, and other ultra small-sized electromechanical devices.
Generally, a MEMS structure includes a CMOS device and a MEMS device. Recently, the integration of complementary metal-oxide semiconductor (CMOS) devices with the MEMS device has been commonly applied. In general, the MEMS device is formed after forming the CMOS device, and then the MEMS device may be integrated with the CMOS device in a manner of a single block. The conventional process of the MEMS device is usually performed after the back end of the CMOS process is finished. In other words, after accomplishing the fabrication of the CMOS device, a dielectric layer and material for the MEMS device are formed on the CMOS device.
However, the material for the MEMS device is usually formed at high manufacturing temperatures, i.e. the material for the MEMS device has a higher growth temperature. Accordingly, the material for the MEMS device with a higher growth temperature is called a thermal stability material. Since the material used after the CMOS device usually has a lower growth temperature, the higher growth temperature for the material in the MEMS device may cause damage to the electrical performance of the CMOS device. Therefore, how to integrate a MEMS device with a CMOS device while providing a good thermal stability material during high temperature processes is an object being actively researched for those skilled in the art.